The invention relates to an exhaust device for a turbine engine.
Turbine engines, for example turbine engines for aircraft, produce a high noise intensity level, which is a quantity of sound which is measured in decibels (dB). A high noise intensity level not only pollutes the environment but is also disadvantageous for the degree of loading of aircraft. After all, the higher the degree of loading, the greater the power which has to be supplied by the turbine engines, which results in a high and sometimes an unacceptable noise intensity level.
A reduction in the noise intensity level of turbine engines is effected, inter alia, by means of a special construction of the turbine engine. Thus, in modern turbine engines only a small portion of the incoming air stream flows through the combustion chambers. The major portion of the incoming air stream is diverted. This diverted air stream rejoins the exhaust gases in the exhaust section. Because, as a result of the high flow rate, the diverted air stream is essentially a turbulent air stream, this results in a reduction in the noise intensity level which is caused by the outgoing air stream from the turbine engine. Nevertheless, a further reduction in the noise intensity level is desirable.
The noise intensity level of turbine engines can also be reduced by fitting a noise-damping material, for example perfolin, in the inlet section of a jet engine. In this case the reduction in the noise intensity level is achieved by so-called quench interference, that is to say the sound waves which penetrate into the sound-damping material extinguish one another by interference. However, these noise-damping materials are not suitable for use in the exhaust section of turbine engines because they are not able to withstand the thermal and mechanical stresses which prevail in the exhaust section. Although noise-damping materials are known which are able to withstand such stresses, these materials have the disadvantage that they are too heavy for use in aviation.
Although some ceramic materials, such as foams, are known which possess noise-damping characteristics, monolithic, ceramic materials of this type have the disadvantage that they have too low a resistance to fatigue and brittle fracture characteristics.